In order to solve the over-charging problem of the EV shell battery, a general solution adopted in the industry is to cut off the main circuit before the cell loses efficacy, so as to prevent the battery from being charged continuously thereby ensuring safety of the battery.
At present, for a square shaped shell battery, a current interrupting device (CID) may be adopted. That is, the positive electrode main circuit includes an air pressure deformable plate and a conductive plate which is integrated with the CID as a whole. The periphery of the conductive plate is connected with an electrode tab of bare cell through welding, the CID portion of the conductive plate is connected with the deformable plate as a whole through welding, and the deformable plate is connected with a positive electrode column through welding so as to conduct a current to a positive electrode terminal.
When a battery is over charged, the internal air pressure is increased, the deformable plate is turned thus tearing the CID, so that the deformable plate is cut off from the conductive plate.
Theoretically, as long as a certain gap exists between the conductive plate and the formable plate or the positive terminal connected with the deformable plate, the main circuit can be cut off after the CID is torn. However, as mentioned above, the conductive plate is integrated with the CID as a whole, and is then fixed with the deformable plate through welding, and the bottom periphery of the conductive plate needs to be welded with the electrode tab of bare cell.
As we known, a certain air pressure is needed to push the deformable plate to tear the CID, both the deformable plate and the CID cannot be made too strong. Relatively speaking, it is preferred to be a little bit weaker. Thus, the conductive plate integrated with the CID as a whole is connected with the deformable plate at the top, and is connected with the electrode tab of bare cell at the bottom, if there is no other component for auxiliary fixing, it is easy to be broken and lose efficacy during the process of normal assembling and using, or the conductive plate is conductively connected with the deformable plate or the top cover plate after being deformed.